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/* Markers: examining, setting and deleting.
   Copyright (C) 1985, 1997 Free Software Foundation, Inc.
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This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING.  If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */
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#include <config.h>
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#include "lisp.h"
#include "buffer.h"
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#include "charset.h"
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/* Record one cached position found recently by
   buf_charpos_to_bytepos or buf_bytepos_to_charpos.  */

static int cached_charpos;
static int cached_bytepos;
static struct buffer *cached_buffer;
static int cached_modiff;

/* Converting between character positions and byte positions.  */

/* There are several places in the buffer where we know
   the corrspondence: BEG, BEGV, PT, GPT, ZV and Z,
   and everywhere there is a marker.  So we find the one of these places
   that is closest to the specified position, and scan from there.  */

/* charpos_to_bytepos returns the byte position corresponding to CHARPOS.  */

/* This macro is a subroutine of charpos_to_bytepos.
   Note that it is desirable that BYTEPOS is not evaluated
   except when we really want its value.  */

#define CONSIDER(CHARPOS, BYTEPOS)					\
{									\
  int this_charpos = (CHARPOS);						\
  int changed = 0;							\
									\
  if (this_charpos == charpos)						\
    return (BYTEPOS);							\
  else if (this_charpos > charpos)					\
    {									\
      if (this_charpos < best_above)					\
	{								\
	  best_above = this_charpos;					\
	  best_above_byte = (BYTEPOS);					\
	  changed = 1;							\
	}								\
    }									\
  else if (this_charpos > best_below)					\
    {									\
      best_below = this_charpos;					\
      best_below_byte = (BYTEPOS);					\
      changed = 1;							\
    }									\
									\
  if (changed)								\
    {									\
      if (best_above - best_below == best_above_byte - best_below_byte)	\
	return best_below_byte + (charpos - best_below);		\
    }									\
}

int
charpos_to_bytepos (charpos)
     int charpos;
{
  return buf_charpos_to_bytepos (current_buffer, charpos);
}

int
buf_charpos_to_bytepos (b, charpos)
     struct buffer *b;
     int charpos;
{
  Lisp_Object tail;
  int gapend_byte = BUF_GPT_BYTE (b) + BUF_GAP_SIZE (b);
  int best_above, best_above_byte;
  int best_below, best_below_byte;

  if (charpos < BUF_BEG (b) || charpos > BUF_Z (b))
    abort ();

  best_above = BUF_Z (b);
  best_above_byte = BUF_Z_BYTE (b);

  /* If this buffer has as many characters as bytes,
     each character must be one byte.
     This takes care of the case where enable-multibyte-characters is nil.  */
  if (best_above == best_above_byte)
    return charpos;

  best_below = 1;
  best_below_byte = 1;

  /* We find in best_above and best_above_byte
     the closest known point above CHARPOS,
     and in best_below and best_below_byte
     the closest known point below CHARPOS,

     If at any point we can tell that the space between those
     two best approximations is all single-byte,
     we interpolate the result immediately.  */

  CONSIDER (BUF_PT (b), BUF_PT_BYTE (b));
  CONSIDER (BUF_GPT (b), BUF_GPT_BYTE (b));
  CONSIDER (BUF_BEGV (b), BUF_BEGV_BYTE (b));
  CONSIDER (BUF_ZV (b), BUF_ZV_BYTE (b));

  if (b == cached_buffer && BUF_MODIFF (b) == cached_modiff)
    CONSIDER (cached_charpos, cached_bytepos);

  tail = BUF_MARKERS (b);
  while (XSYMBOL (tail) != XSYMBOL (Qnil))
    {
      int i = XMARKER (tail)->bufpos;
      CONSIDER (XMARKER (tail)->charpos,
		(i > gapend_byte ? i - BUF_GAP_SIZE (b)
		 : i > BUF_GPT_BYTE (b) ? BUF_GPT_BYTE (b)
		 : i));

      /* If we are down to a range of 50 chars,
	 don't bother checking any other markers;
	 scan the intervening chars directly now.  */
      if (best_above - best_below < 50)
	break;

      tail = XMARKER (tail)->chain;
    }

  /* We get here if we did not exactly hit one of the known places.
     We have one known above and one known below.
     Scan, counting characters, from whichever one is closer.  */

  if (charpos - best_below < best_above - charpos)
    {
      int record = charpos - best_below > 5000;

      while (best_below != charpos)
	{
	  best_below++;
	  BUF_INC_POS (b, best_below_byte);
	}

      /* If this position is quite far from the nearest known position,
	 cache the correspondence by creating a marker here.
	 It will last until the next GC.  */
      if (record)
	{
	  Lisp_Object marker;
	  marker = Fmake_marker ();
	  set_marker_both (marker, Qnil, best_below, best_below_byte);
	}

      cached_buffer = b;
      cached_modiff = BUF_MODIFF (b);
      cached_charpos = best_below;
      cached_bytepos = best_below_byte;

      return best_below_byte;
    }
  else
    {
      int record = best_above - charpos > 5000;

      while (best_above != charpos)
	{
	  best_above--;
	  BUF_DEC_POS (b, best_above_byte);
	}

      /* If this position is quite far from the nearest known position,
	 cache the correspondence by creating a marker here.
	 It will last until the next GC.  */
      if (record)
	{
	  Lisp_Object marker;
	  marker = Fmake_marker ();
	  set_marker_both (marker, Qnil, best_above, best_above_byte);
	}

      cached_buffer = b;
      cached_modiff = BUF_MODIFF (b);
      cached_charpos = best_above;
      cached_bytepos = best_above_byte;

      return best_above_byte;
    }
}

#undef CONSIDER

/* bytepos_to_charpos returns the char position corresponding to BYTEPOS.  */

/* This macro is a subroutine of bytepos_to_charpos.
   It is used when BYTEPOS is actually the byte position.  */

#define CONSIDER(BYTEPOS, CHARPOS)					\
{									\
  int this_bytepos = (BYTEPOS);						\
  int changed = 0;							\
									\
  if (this_bytepos == bytepos)						\
    return (CHARPOS);							\
  else if (this_bytepos > bytepos)					\
    {									\
      if (this_bytepos < best_above_byte)				\
	{								\
	  best_above = (CHARPOS);					\
	  best_above_byte = this_bytepos;				\
	  changed = 1;							\
	}								\
    }									\
  else if (this_bytepos > best_below_byte)				\
    {									\
      best_below = (CHARPOS);						\
      best_below_byte = this_bytepos;					\
      changed = 1;							\
    }									\
									\
  if (changed)								\
    {									\
      if (best_above - best_below == best_above_byte - best_below_byte)	\
	return best_below + (bytepos - best_below_byte);		\
    }									\
}

int
bytepos_to_charpos (bytepos)
     int bytepos;
{
  return buf_bytepos_to_charpos (current_buffer, bytepos);
}

int
buf_bytepos_to_charpos (b, bytepos)
     struct buffer *b;
     int bytepos;
{
  Lisp_Object tail;
  int best_above, best_above_byte;
  int best_below, best_below_byte;

  if (bytepos < BUF_BEG_BYTE (b) || bytepos > BUF_Z_BYTE (b))
    abort ();

  best_above = BUF_Z (b);
  best_above_byte = BUF_Z_BYTE (b);

  /* If this buffer has as many characters as bytes,
     each character must be one byte.
     This takes care of the case where enable-multibyte-characters is nil.  */
  if (best_above == best_above_byte)
    return bytepos;

  best_below = 1;
  best_below_byte = 1;

  CONSIDER (BUF_PT_BYTE (b), BUF_PT (b));
  CONSIDER (BUF_GPT_BYTE (b), BUF_GPT (b));
  CONSIDER (BUF_BEGV_BYTE (b), BUF_BEGV (b));
  CONSIDER (BUF_ZV_BYTE (b), BUF_ZV (b));

  if (b == cached_buffer && BUF_MODIFF (b) == cached_modiff)
    CONSIDER (cached_bytepos, cached_charpos);

  tail = BUF_MARKERS (b);
  while (XSYMBOL (tail) != XSYMBOL (Qnil))
    {
      int marker_bytepos = XMARKER (tail)->bufpos;

      if (marker_bytepos > BUF_GPT_BYTE (b) + BUF_GAP_SIZE (b))
	marker_bytepos -= BUF_GAP_SIZE (b);
      else if (marker_bytepos > BUF_GPT_BYTE (b))
	marker_bytepos = BUF_GPT_BYTE (b);

      CONSIDER (marker_bytepos, XMARKER (tail)->charpos);

      /* If we are down to a range of 50 chars,
	 don't bother checking any other markers;
	 scan the intervening chars directly now.  */
      if (best_above - best_below < 50)
	break;

      tail = XMARKER (tail)->chain;
    }

  /* We get here if we did not exactly hit one of the known places.
     We have one known above and one known below.
     Scan, counting characters, from whichever one is closer.  */

  if (bytepos - best_below_byte < best_above_byte - bytepos)
    {
      int record = best_above_byte - bytepos > 5000;

      while (best_below_byte < bytepos)
	{
	  best_below++;
	  BUF_INC_POS (b, best_below_byte);
	}

      /* If this position is quite far from the nearest known position,
	 cache the correspondence by creating a marker here.
	 It will last until the next GC.  */
      if (record)
	{
	  Lisp_Object marker;
	  marker = Fmake_marker ();
	  set_marker_both (marker, Qnil, best_below, best_below_byte);
	}

      cached_buffer = b;
      cached_modiff = BUF_MODIFF (b);
      cached_charpos = best_below;
      cached_bytepos = best_below_byte;

      return best_below;
    }
  else
    {
      int record = best_above_byte - bytepos > 5000;

      while (best_above_byte > bytepos)
	{
	  best_above--;
	  BUF_DEC_POS (b, best_above_byte);
	}

      /* If this position is quite far from the nearest known position,
	 cache the correspondence by creating a marker here.
	 It will last until the next GC.  */
      if (record)
	{
	  Lisp_Object marker;
	  marker = Fmake_marker ();
	  set_marker_both (marker, Qnil, best_above, best_above_byte);
	}

      cached_buffer = b;
      cached_modiff = BUF_MODIFF (b);
      cached_charpos = best_above;
      cached_bytepos = best_above_byte;

      return best_above;
    }
}

#undef CONSIDER

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/* Operations on markers. */

DEFUN ("marker-buffer", Fmarker_buffer, Smarker_buffer, 1, 1, 0,
  "Return the buffer that MARKER points into, or nil if none.\n\
Returns nil if MARKER points into a dead buffer.")
  (marker)
     register Lisp_Object marker;
{
  register Lisp_Object buf;
  CHECK_MARKER (marker, 0);
  if (XMARKER (marker)->buffer)
    {
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      XSETBUFFER (buf, XMARKER (marker)->buffer);
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      /* Return marker's buffer only if it is not dead.  */
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      if (!NILP (XBUFFER (buf)->name))
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	return buf;
    }
  return Qnil;
}

DEFUN ("marker-position", Fmarker_position, Smarker_position, 1, 1, 0,
  "Return the position MARKER points at, as a character number.")
  (marker)
     Lisp_Object marker;
{
  register Lisp_Object pos;
  register int i;
  register struct buffer *buf;

  CHECK_MARKER (marker, 0);
  if (XMARKER (marker)->buffer)
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    return make_number (XMARKER (marker)->charpos);
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  return Qnil;
}
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DEFUN ("set-marker", Fset_marker, Sset_marker, 2, 3, 0,
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  "Position MARKER before character number POSITION in BUFFER.\n\
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BUFFER defaults to the current buffer.\n\
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If POSITION is nil, makes marker point nowhere.\n\
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Then it no longer slows down editing in any buffer.\n\
Returns MARKER.")
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  (marker, position, buffer)
     Lisp_Object marker, position, buffer;
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{
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  register int charno, bytepos;
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  register struct buffer *b;
  register struct Lisp_Marker *m;

  CHECK_MARKER (marker, 0);
  /* If position is nil or a marker that points nowhere,
     make this marker point nowhere.  */
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  if (NILP (position)
      || (MARKERP (position) && !XMARKER (position)->buffer))
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    {
      unchain_marker (marker);
      return marker;
    }

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  if (NILP (buffer))
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    b = current_buffer;
  else
    {
      CHECK_BUFFER (buffer, 1);
      b = XBUFFER (buffer);
      /* If buffer is dead, set marker to point nowhere.  */
      if (EQ (b->name, Qnil))
	{
	  unchain_marker (marker);
	  return marker;
	}
    }

  m = XMARKER (marker);

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  /* Optimize the special case where we are copying the position
     of an existing marker, and MARKER is already in the same buffer.  */
  if (MARKERP (position) && b == XMARKER (position)->buffer
      && b == m->buffer)
    {
      m->bufpos = XMARKER (position)->bufpos;
      m->charpos = XMARKER (position)->charpos;
      return marker;
    }

  CHECK_NUMBER_COERCE_MARKER (position, 1);

  charno = XINT (position);

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  if (charno < BUF_BEG (b))
    charno = BUF_BEG (b);
  if (charno > BUF_Z (b))
    charno = BUF_Z (b);
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  bytepos = buf_charpos_to_bytepos (b, charno);

  /* Every character is at least one byte.  */
  if (charno > bytepos)
    abort ();

  if (bytepos > BUF_GPT_BYTE (b))
    bytepos += BUF_GAP_SIZE (b);

  m->bufpos = bytepos;
  m->charpos = charno;
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  if (m->buffer != b)
    {
      unchain_marker (marker);
      m->buffer = b;
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      m->chain = BUF_MARKERS (b);
      BUF_MARKERS (b) = marker;
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    }
  
  return marker;
}

/* This version of Fset_marker won't let the position
   be outside the visible part.  */

Lisp_Object 
set_marker_restricted (marker, pos, buffer)
     Lisp_Object marker, pos, buffer;
{
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  register int charno, bytepos;
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  register struct buffer *b;
  register struct Lisp_Marker *m;

  CHECK_MARKER (marker, 0);
  /* If position is nil or a marker that points nowhere,
     make this marker point nowhere.  */
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  if (NILP (pos)
      || (MARKERP (pos) && !XMARKER (pos)->buffer))
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    {
      unchain_marker (marker);
      return marker;
    }

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  if (NILP (buffer))
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    b = current_buffer;
  else
    {
      CHECK_BUFFER (buffer, 1);
      b = XBUFFER (buffer);
      /* If buffer is dead, set marker to point nowhere.  */
      if (EQ (b->name, Qnil))
	{
	  unchain_marker (marker);
	  return marker;
	}
    }

  m = XMARKER (marker);

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  /* Optimize the special case where we are copying the position
     of an existing marker, and MARKER is already in the same buffer.  */
  if (MARKERP (pos) && b == XMARKER (pos)->buffer
      && b == m->buffer)
    {
      m->bufpos = XMARKER (pos)->bufpos;
      m->charpos = XMARKER (pos)->charpos;
      return marker;
    }

  CHECK_NUMBER_COERCE_MARKER (pos, 1);

  charno = XINT (pos);

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  if (charno < BUF_BEGV (b))
    charno = BUF_BEGV (b);
  if (charno > BUF_ZV (b))
    charno = BUF_ZV (b);
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  bytepos = buf_charpos_to_bytepos (b, charno);

  /* Every character is at least one byte.  */
  if (charno > bytepos)
    abort ();

  if (bytepos > BUF_GPT_BYTE (b))
    bytepos += BUF_GAP_SIZE (b);

  m->bufpos = bytepos;
  m->charpos = charno;
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  if (m->buffer != b)
    {
      unchain_marker (marker);
      m->buffer = b;
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      m->chain = BUF_MARKERS (b);
      BUF_MARKERS (b) = marker;
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    }
  
  return marker;
}
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/* Set the position of MARKER, specifying both the
   character position and the corresponding byte position.  */
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Lisp_Object 
set_marker_both (marker, buffer, charpos, bytepos)
     Lisp_Object marker, buffer;
     int charpos, bytepos;
{
  register struct buffer *b;
  register struct Lisp_Marker *m;

  CHECK_MARKER (marker, 0);
  /* If position is nil or a marker that points nowhere,
     make this marker point nowhere.  */
  if (NILP (charpos)
      || (MARKERP (charpos) && !XMARKER (charpos)->buffer))
    {
      unchain_marker (marker);
      return marker;
    }

  CHECK_NUMBER_COERCE_MARKER (charpos, 1);
  if (NILP (buffer))
    b = current_buffer;
  else
    {
      CHECK_BUFFER (buffer, 1);
      b = XBUFFER (buffer);
      /* If buffer is dead, set marker to point nowhere.  */
      if (EQ (b->name, Qnil))
	{
	  unchain_marker (marker);
	  return marker;
	}
    }

  m = XMARKER (marker);

  /* In a single-byte buffer, the two positions must be equal.  */
  if (BUF_Z (b) == BUF_Z_BYTE (b)
      && charpos != bytepos)
    abort ();
  /* Every character is at least one byte.  */
  if (charpos > bytepos)
    abort ();

  if (bytepos > BUF_GPT_BYTE (b))
    bytepos += BUF_GAP_SIZE (b);

  m->bufpos = bytepos;
  m->charpos = charpos;

  if (m->buffer != b)
    {
      unchain_marker (marker);
      m->buffer = b;
      m->chain = BUF_MARKERS (b);
      BUF_MARKERS (b) = marker;
    }
  
  return marker;
}

/* This version of set_marker_both won't let the position
   be outside the visible part.  */

Lisp_Object 
set_marker_restricted_both (marker, buffer, charpos, bytepos)
     Lisp_Object marker, buffer;
     int charpos, bytepos;
{
  register struct buffer *b;
  register struct Lisp_Marker *m;

  CHECK_MARKER (marker, 0);

  if (NILP (buffer))
    b = current_buffer;
  else
    {
      CHECK_BUFFER (buffer, 1);
      b = XBUFFER (buffer);
      /* If buffer is dead, set marker to point nowhere.  */
      if (EQ (b->name, Qnil))
	{
	  unchain_marker (marker);
	  return marker;
	}
    }

  m = XMARKER (marker);

  if (charpos < BUF_BEGV (b))
    charpos = BUF_BEGV (b);
  if (charpos > BUF_ZV (b))
    charpos = BUF_ZV (b);
  if (bytepos < BUF_BEGV_BYTE (b))
    bytepos = BUF_BEGV_BYTE (b);
  if (bytepos > BUF_ZV_BYTE (b))
    bytepos = BUF_ZV_BYTE (b);

  /* In a single-byte buffer, the two positions must be equal.  */
  if (BUF_Z (b) == BUF_Z_BYTE (b)
      && charpos != bytepos)
    abort ();
  /* Every character is at least one byte.  */
  if (charpos > bytepos)
    abort ();

  if (bytepos > BUF_GPT_BYTE (b))
    bytepos += BUF_GAP_SIZE (b);

  m->bufpos = bytepos;
  m->charpos = charpos;

  if (m->buffer != b)
    {
      unchain_marker (marker);
      m->buffer = b;
      m->chain = BUF_MARKERS (b);
      BUF_MARKERS (b) = marker;
    }
  
  return marker;
}

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/* This is called during garbage collection,
   so we must be careful to ignore and preserve mark bits,
   including those in chain fields of markers.  */

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void
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unchain_marker (marker)
     register Lisp_Object marker;
{
  register Lisp_Object tail, prev, next;
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  register EMACS_INT omark;
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  register struct buffer *b;

  b = XMARKER (marker)->buffer;
  if (b == 0)
    return;

  if (EQ (b->name, Qnil))
    abort ();

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  tail = BUF_MARKERS (b);
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  prev = Qnil;
  while (XSYMBOL (tail) != XSYMBOL (Qnil))
    {
      next = XMARKER (tail)->chain;
      XUNMARK (next);

      if (XMARKER (marker) == XMARKER (tail))
	{
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	  if (NILP (prev))
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	    {
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	      BUF_MARKERS (b) = next;
	      /* Deleting first marker from the buffer's chain.  Crash
		 if new first marker in chain does not say it belongs
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		 to the same buffer, or at least that they have the same
		 base buffer.  */
	      if (!NILP (next) && b->text != XMARKER (next)->buffer->text)
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		abort ();
	    }
	  else
	    {
	      omark = XMARKBIT (XMARKER (prev)->chain);
	      XMARKER (prev)->chain = next;
	      XSETMARKBIT (XMARKER (prev)->chain, omark);
	    }
	  break;
	}
      else
	prev = tail;
      tail = next;
    }
  XMARKER (marker)->buffer = 0;
}

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/* Return the char position of marker MARKER, as a C integer.  */
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int
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marker_position (marker)
     Lisp_Object marker;
{
  register struct Lisp_Marker *m = XMARKER (marker);
  register struct buffer *buf = m->buffer;
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  if (!buf)
    error ("Marker does not point anywhere");

  return m->charpos;
}

/* Return the byte position of marker MARKER, as a C integer.  */

int
marker_byte_position (marker)
     Lisp_Object marker;
{
  register struct Lisp_Marker *m = XMARKER (marker);
  register struct buffer *buf = m->buffer;
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  register int i = m->bufpos;

  if (!buf)
    error ("Marker does not point anywhere");

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  if (i > BUF_GPT_BYTE (buf) + BUF_GAP_SIZE (buf))
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    i -= BUF_GAP_SIZE (buf);
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  else if (i > BUF_GPT_BYTE (buf))
    i = BUF_GPT_BYTE (buf);
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  if (i < BUF_BEG_BYTE (buf) || i > BUF_Z_BYTE (buf))
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    abort ();

  return i;
}
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DEFUN ("copy-marker", Fcopy_marker, Scopy_marker, 1, 2, 0,
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  "Return a new marker pointing at the same place as MARKER.\n\
If argument is a number, makes a new marker pointing\n\
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at that position in the current buffer.\n\
The optional argument TYPE specifies the insertion type of the new marker;\n\
see `marker-insertion-type'.")
  (marker, type)
     register Lisp_Object marker, type;
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{
  register Lisp_Object new;

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  if (INTEGERP (marker) || MARKERP (marker))
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    {
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      new = Fmake_marker ();
      Fset_marker (new, marker,
		   (MARKERP (marker) ? Fmarker_buffer (marker) : Qnil));
      XMARKER (new)->insertion_type = !NILP (type);
      return new;
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    }
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  else
    marker = wrong_type_argument (Qinteger_or_marker_p, marker);
}

DEFUN ("marker-insertion-type", Fmarker_insertion_type,
       Smarker_insertion_type, 1, 1, 0,
  "Return insertion type of MARKER: t if it stays after inserted text.\n\
nil means the marker stays before text inserted there.")
  (marker)
     register Lisp_Object marker;
{
  register Lisp_Object buf;
  CHECK_MARKER (marker, 0);
  return XMARKER (marker)->insertion_type ? Qt : Qnil;
}

DEFUN ("set-marker-insertion-type", Fset_marker_insertion_type,
       Sset_marker_insertion_type, 2, 2, 0,
  "Set the insertion-type of MARKER to TYPE.\n\
If TYPE is t, it means the marker advances when you insert text at it.\n\
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If TYPE is nil, it means the marker stays behind when you insert text at it.")
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  (marker, type)
     Lisp_Object marker, type;
{
  CHECK_MARKER (marker, 0);

  XMARKER (marker)->insertion_type = ! NILP (type);
  return type;
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}
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DEFUN ("buffer-has-markers-at", Fbuffer_has_markers_at, Sbuffer_has_markers_at,
  1, 1, 0,
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  "Return t if there are markers pointing at POSITION in the current buffer.")
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  (position)
      Lisp_Object position;
{
  register Lisp_Object tail;
  register int charno;

  charno = XINT (position);

  if (charno < BEG)
    charno = BEG;
  if (charno > Z)
    charno = Z;

  for (tail = BUF_MARKERS (current_buffer);
       XSYMBOL (tail) != XSYMBOL (Qnil);
       tail = XMARKER (tail)->chain)
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    if (XMARKER (tail)->charpos == charno)
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      return Qt;

  return Qnil;
}
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void
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syms_of_marker ()
{
  defsubr (&Smarker_position);
  defsubr (&Smarker_buffer);
  defsubr (&Sset_marker);
  defsubr (&Scopy_marker);
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  defsubr (&Smarker_insertion_type);
  defsubr (&Sset_marker_insertion_type);
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  defsubr (&Sbuffer_has_markers_at);
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}